/*
 * Copyright 2012-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.context.embedded.tomcat;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.boot.web.servlet.ServletContextInitializer;

import javax.servlet.ServletContainerInitializer;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import java.util.Set;

/**
 * {@link ServletContainerInitializer} used to trigger {@link ServletContextInitializer
 * ServletContextInitializers} and track startup errors.
 *
 * @author Phillip Webb
 * @author Andy Wilkinson
 * @since 1.2.1
 */
class TomcatStarter implements ServletContainerInitializer
{

    private static final Log logger = LogFactory.getLog(TomcatStarter.class);

    private final ServletContextInitializer[] initializers;

    private volatile Exception startUpException;

    TomcatStarter(ServletContextInitializer[] initializers)
    {
        this.initializers = initializers;
    }

    /**
     * TomcatStarter相当于hook了context启动的事件
     *
     * @param classes
     * @param servletContext
     * @throws ServletException
     */
    @Override
    public void onStartup(Set<Class<?>> classes, ServletContext servletContext) throws ServletException
    {
        try
        {
            for (ServletContextInitializer initializer : this.initializers)
            {
                initializer.onStartup(servletContext);
            }
        }
        catch (Exception ex)
        {
            this.startUpException = ex;
            // Prevent Tomcat from logging and re-throwing when we know we can
            // deal with it in the main thread, but log for information here.
            if (logger.isErrorEnabled())
            {
                logger.error("Error starting Tomcat context. Exception: " + ex.getClass().getName() + ". Message: " +
                                     ex.getMessage());
            }
        }
    }

    public Exception getStartUpException()
    {
        return this.startUpException;
    }

}
